The RECCE Pro would be an optically enhanced milling monocular, providing the same handy reticle ranging feature, but with a higher degree of optical quality, resulting in brighter, sharper images, and improved low-light performance. The RECCE also features a helical focus mechanism that is centrally located on the body of the optic, and is a bit easier to manipulate and access!
To add more to the answer from Vortex.
This is able to focus to 16.4ft. The Recce is able to focus to 5ft.
The Recce has an armor tex protective covering. This does not.
This Tactical RT is simply a Solo, with the Recce's reticle.
The Recce's glass is superior. The coatings on the glass are stronger. The Recce is more suited for Police/combat related roles. It is a more robust monocular overall.
This Tactical RT has a longer focal length and is slightly brighter.
For everyday non combat use. The Tactical RT will do what anybody needs, except focusing close. Vortex has a fantastic warranty. If it breaks, they will replace it.
The Recce will also do what anybody needs. It's less likely to break, it was made to be less likely to break. it's not going to be up to vortex's actual military grade bomb proof stuff. But it's also not $3-4k.
They are both great deals.
If you have a high end $2k scope. You will notice the difference between the 2 monoculars. Not because the Solo RT is bad. But because you know the difference between high end glass and mid grade glass. Does it matter? That's up to you.